1. Field of the Invention
The invention relates to reprocessing of non-biodegradable materials and particularly to reprocessing of rubber containing material. More particularly the invention relates to reprocessing rubber materials, especially waste tires, by a heat treatment and using a proportion of coal and, optionally, a catalyst.
2. Description of Prior Art
In the past years environmental provisions have become increasingly restrictive with regard to the littering and processing of non-biodegradable waste materials. The restrictions have lead to an increasing interest in reprocessing and recycling waste materials as plastics, paper, rubber and other combustible materials, into new, re-usable and valuable materials and products, instead of simply burning such waste materials as done throughout many decades.
Rubber-containing waste materials and especially tires, arise in enormous quantities and a large if not major portion thereof is at present still being simply littered or burned, whereby, environmental damages are caused and potentially valuable components are not recovered.
A way of reprocessing plastics, paper, rubber and other substantially combustible materials which is becoming of increasing interest, is related to coprocessing these materials with coal. An overview of such coprocessing methods is given in "Co-Utilization of Coal and Waste Materials"; American Chemical Society (ACS), Division of Fuel Chemistry; Vol. 40, 1 (1995).
Various systems for co-processing coal with waste materials are available at present. Thus, Huggins et al.; Energy and Fuels, vol. 8, page 1228 (1994) have described a method according to which waste plastic from juice bottles, milk bottles and other similar materials, are processed by coal liquefaction, whereby oils are obtained. Similar methods using coal liquefaction to obtain synthetic oils from co-processing waste tires and coal, are described by Anderson et al.; ACS; Vol. 38, 3 (1993) and in U.S. Pat. No. 5,061,363.
Another method, by which carbon and rubber are liquefied in the presence of a solvent and resulting in acceptable yields in synthetic oils, has been described by Liu et al., Energy and Fuels; Vol. 8, 607 (1994).
Methods according to which waste materials are subjected to pyrolysis have been described by Williams et al.; Proceeding of the Institution of Mechanical Engineers, Part C, 55, 207 (1993) relating to the economic aspects of the subjecting waste tires to pyrolysis, and by Font et al.; Energy and Fules, Vol. 8, page 1238 (1994) referring to pyrolysis of plastics in an inert atmosphere.
The hereabove mentioned known methods for processing waste rubber materials and especially waste tires have not been entirely satisfactory inasmuch they require relatively high inputs of energy or, especially in the case of coal-liquefaction based processes, are rather complex.